If we live in $4+n$ dimension and compactify the extra $n$ dimensions so that they are of typical size $R$, then on scales $r\gg R$ gravity is known to act in the normal manner. That is, the ...
I have some questions with string theory: Why is it that there is exactly 4 large spacetime dimensions while the rest remain small? It is a nonlocal QFT. How could that fit in GR?
Is time dilation a form of dimensional compactification? As a probe approaches a black hole, toward a point on the equator of the event horizon, does general relativity predict that the time ...
I've been very impressed to learn about kaluza-klein theory and compactification strategies. I would like to read more about this but in the meantime i'm curious about 2 different points. I have the ...
What is the exact shape of the universe? I know of the balloon analogy, and the bread with raisins in it. These clarify some points, like how the universe can have no centre, and how it can expand ...